Many mechanical systems, such as commercial vehicles, manufacturing equipment, and other industrial systems, may be exposed to particularly energetic conditions, such as vibration, temperature extremes, impacts, or mechanical stresses. For example, even when on the ground aircraft may be exposed to significant stresses during cargo loading and unloading, as well as impacts from support vehicles and ground support equipment. During flight, stresses and/or impacts may result from shifting or improperly secured cargo. In addition, some system components may undergo thermal degradation when exposed to high temperatures. For example, some composite materials may be affected by thermal degradation, which may compromise the mechanical properties of the composite, including flexural strength, compression after impact, and interlaminar shear strength, among others.
It is therefore not uncommon for selected components of various industrial systems to be routinely inspected and evaluated during the operational lifetime of the component. Unfortunately, the integrity of one or more system components may be compromised without any accompanying visually detectable indication. In such cases a potentially damaged component may remain in service until a scheduled examination, or until it fails. Accordingly, there is a need for a non-destructive inspection technique that may readily and inexpensively indicate whether a system component has been subjected to an energetic event such as an impact and/or damaging high temperatures during operation. Such an indication may then trigger further evaluation of the system component, or even its replacement.